This disclosure relates to methods of servicing a wellbore. More specifically, it relates to methods of modifying the permeability of a portion of a subterranean formation.
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed.
Subsequently, oil or gas residing in the subterranean formation may be recovered by driving the fluid into the well using, for example, a pressure gradient that exists between the formation and the wellbore, the force of gravity, displacement of the fluid using a pump or the force of another fluid injected into the well or an adjacent well. The production of the fluid in the formation may be increased by hydraulically fracturing the formation. That is, a viscous fracturing fluid may be pumped down the casing to the formation at a rate and a pressure sufficient to form fractures that extend into the formation, providing additional pathways through which the oil or gas can flow to the well. Unfortunately, water along with oil or gas may eventually be produced by the formation through the fractures therein. In such cases, the formation may be treated with a relative permeability modifier (RPM) that is meant to control water production, shut off water-producing intervals, and/or enhance hydrocarbon production. A challenge to the use of conventional RPMs is that they do not adhere strongly to the formation surface, and consequently are not effective long term. Thus, an ongoing need exists for more effective compositions and methods for utilizing RPMs in subterranean formations.